‘The Parisian press called the assassination of the twenty-nine-year-old Italian widow, Laetitia Toureaux a perfect crime,’ begin the authors of this book. After spending a Sunday afternoon at a dance hall, Toureaux boarded the Métro and took a place in an otherwise empty first-class carriage:

At 6.27pm the train left the station. When it arrived less than sixty seconds later at its next stop, Toureaux was dying, an eight-inch dagger buried to its hilt in her neck. She expired before she could identify her killer, who had managed to enter the car, attack her, and flee unseen from the Métro station.